Enable overriding location image name with CS_IMAGE_DISPLAY_NAME

What does this MR do?

With the implementation of Support tar file scanning (!3151 - merged) we may get scans of tar files. This results in location images set to .tar paths. This may not be ideal for some users. This MR adds support for CS_IMAGE_DISPLAY_NAME which enables users to override the location image name with their own specified name.

Note that this is already technically possible by:

1. Retagging an image with whatever name one wishes.
2. If scanning a tar, naming it however one wishes (it doesn't have to end in .tar).

This addition makes the process easier.

What are the relevant issue numbers / merge requests ?

Does this MR meet the acceptance criteria?

• Changelog entry added
• Documentation created/updated for GitLab EE, if necessary
• Documentation created/updated for this project, if necessary
• Documentation reviewed by technical writer or follow-up review issue created
• Tests added
• Job definition updated, if necessary
  • Auto-DevOps template
  • Job definition example
  • CI Templates
• Conforms to the code review guidelines
• Conforms to the Go guidelines
• Conforms to the Ruby guidelines
• Security reports checked/validated by reviewer